diff --git a/programs/pkey/pk_verify.c b/programs/pkey/pk_verify.c
index 55f977c..88ad575 100644
--- a/programs/pkey/pk_verify.c
+++ b/programs/pkey/pk_verify.c
@@ -29,6 +29,7 @@
 #if defined(POLARSSL_PLATFORM_C)
 #include "polarssl/platform.h"
 #else
+#define polarssl_snprintf   snprintf
 #define polarssl_printf     printf
 #endif
 
@@ -94,7 +95,7 @@
      * Extract the signature from the text file
      */
     ret = 1;
-    snprintf( filename, sizeof(filename), "%s.sig", argv[2] );
+    polarssl_snprintf( filename, sizeof(filename), "%s.sig", argv[2] );
 
     if( ( f = fopen( filename, "rb" ) ) == NULL )
     {